This invention relates to improvements in internal combustion engines of the so-called "uncooled" type. Such engines are sometimes termed low heat rejection engines. In the past such engines were termed "adiabatic" engines.
The above type engines have included insulator coatings on the combustion chamber surfaces, as shown for example in U.S. Pat. No. 4,074,671 to S. Pennila. Such coatings, have been used to reduce heat rejection from the combustion chamber into the engine walls (e.g., cylinder block and cylinder head), thereby retaining heat within the chamber for achieving an increased thermal efficiency. The insulator coatings have been applied to the chamber surfaces by the plasma spray process. Unfortunately the mechanical durability of such coatings is not entirely satisfactory when the coatings are of sufficient thickness to offer appreciable resistance to heat flow; when the coating thickness is greater than about 0.040 inch the erosion forces and high temperatures in the combustion chamber tend to cause a mechanical breakdown of the coating.
The present invention relates to mechanisms for shielding the insulator coatings from erosion forces and friction (wear) forces that occur during engine operations. The shielding mechanisms preferably take the form of separately-formed components applied to the engine surfaces after the insulator coatings have been formed on such engine surfaces.
Use of the shielding mechanisms enables thicker coatings to be applied to the engine surfaces because the coatings are no longer exposed to erosion-friction forces that tend to destruct the thicker coatings. The thicker insulator coatings provide a greater thermal insulation action, thereby making possible greater engine thermal efficiency.
The invention is used in low heat rejection diesel engines of the adiabatic type, i.e., uncooled engines that are not water-cooled or air-cooled
The single FIGURE of the drawing shows one cylinder of a multi-cylinder engine embodying my invention. The other cylinders would be similarly constructed.